Abstract: Fiber cement material, which contains organic fibers, is used as an additional raw material for the production of cement clinker. The cement clinker is produced in a system which comprises a cyclone tower (11) and a rotating drum kiln (15). The cyclone tower (11) comprises cyclones (1-5) and a pre-calciner unit (10) wherein fuel is combusted to feed the cyclone tower with heat. The raw clinker meal is passed through the cyclone tower to preheat it. By the combustion of the fuel in the pre-calciner unit (10) a hot zone is produced in the cyclone tower wherein the raw clinker meal is calcined.